Yes, there are wrong ways to teach grammar. A grammar lesson goes wrong when students get no reason to learn a rule, too little practice, too much focus on form over meaning, or a teacher who expects perfect English. Here is what works better.
Any ESL teacher knows that if you want students to have a good grasp of English, you need to drill the grammar basics. However, few ESL teachers smile when it is time to teach grammar.
Grammar is an indispensable part of any language, of course. But the old way of teaching it, by making students memorize rules and diagrams, does not work well. Or does it? Is there such a thing as a wrong way to teach grammar?
It turns out that there are "wrong" ways to teach grammar. Here are 4 of them.
1. Not giving any motivation
Why do your students need to learn the past tense? Because it is in the syllabus? That is hardly a motivation.
Lack of motivation is not a problem of language teaching alone. Chat with students, and you will learn that teachers rarely explain why they should learn a subject at all. What do I need the Pythagorean theorem for? Is there any point in learning about World War II? How will learning about enzymes help me get a job?
Do your best to give students reasons to learn. When you teach the past tense, tell them that it is the natural way to talk about events that have already happened, and that many novels are written in it.
2. Too little practice
When teachers are chasing deadlines, it is common to make students memorize a concept, give a test, and move on to the next grammar lesson. As a result, students have very little chance to internalize what they have just learned.
It is better to use earlier lessons again in daily conversation and in later lessons. For instance, as an icebreaker, ask students what they ate for breakfast and have them answer in the past tense.
3. Focusing on grammar instead of meaning
"Isn't the point of teaching grammar to focus on grammar?" you may ask.
That is true, but remember that the point of language is to get a message across. If your students have trouble with prepositions and write something like "the clock is at the wall", it is not a disaster. Everybody still understands what it means, and you can show them that the clock is on the wall without stopping the conversation.
4. Expecting students to produce perfect English
ESL teachers need to accept that if their students could already speak perfect English, they would not be in the class.
Your students are there to learn English. You will need to correct their grammar, but not every mistake. That might sound strange, but correcting every single mistake is counterproductive. It scares students, and they become reluctant to speak up in class. Focus on the most glaring and frequent mistakes. (There is more on this in how to give effective feedback on students' writing.)
Let students fix the minor mistakes as they go. For instance, you can point them to the Spell Checker, which marks spelling and grammar mistakes and explains each one, so they can find and fix their own errors. For the wider question, see should grammar be taught in ESL classes?